In general, we are interested in the cellular mechanisms which guide the establishment and maintenance of synaptic connections at the neuromuscular junction. There are two projects of current interest. 1) We are studying the elimination of synapses which normally occurs in newborn rats. At the present time, we are investigating the effects of de-afferentation and spinal cord transection on this process in newborn rats. In the future, we hope to study the effects of altered electrical activity in motor nerves on the synaptic elimination process. 2) We are also studying the formation of nerve-muscle synapses in tissue culture. We are using a new preparation in which adult muscle fibers are re-innervated in culture by spinal cord neurons. One particular question of interest is whether the original synaptic site will become preferentially re-innervated, or whether the synapses will form essentially anywhere on the surface of the muscle fibers.